This invention relates to a curing envelope spreader for use in a tire retreading process and an associated method.
Retreading of tires, especially large truck and bus tires, is an economical and efficient way to get more life out of a tire and is becoming more and more prevalent as new truck and bus tires become more expensive. In one type of tire retreading process, the used vehicle tire is brought to a retreading shop and the old tread is removed and the tire casing is conditioned to receive the new tread. See, e.g., U.S. Pat. No. 3,728,181. Once the new tread is placed on the tire casing a curing envelope is placed around the retreaded tire. See U.S. Pat. Nos. 4,203,793; 4,434,018; and 4,634,357. The retreaded tire, which is now surrounded by the curing envelope, is then placed in a curing chamber where a combination of time, pressure and temperature are used to securely bond the tread of the casing. See U.S. Pat. No. 4,201,610. All patents referenced to herein are expressly incorporated by reference.
In large retreading shops, the tires are moved from place to place by the use of an overhead monorail from which a hook can be hung. The hook engages the tire and the overhead monorail system moves the tire from, for example, the retreading station to the curing chamber. The monorail system speeds along the retreading process and reduces work-related injuries. This increases productivity while at the same time reducing costs.
In the monorail system, it is advantageous to minimize the number of times the tire has to be removed from the hook to be worked on and then placed back on the hook to be moved to a different station. This is because manual operator labor can be avoided, with its attendant costs and productivity losses. Less manual labor also reduces the possibility of operator injury from lifting and moving of the tires.
With current retreading systems, the tire is removed from the hook in order to either place the curing envelope on the tire or remove the curing envelope from the tire after curing or both. Furthermore, the curing envelope is usually placed on and removed from the tire manually. This is strenuous, difficult and repetitive manual labor. Thus, there is not only low productivity but also the possibility of operator injury with current processes where manual labor is used to place on and/or remove the curing envelope from the tire.
What is needed, therefore, is an efficient and effective way to safely and easily place a curing envelope onto a retreaded tire and then remove the curing envelope from the retreaded tire after curing without the need for manual labor. Furthermore, the curing envelope should be able to be placed on or removed from the tire without a major disruption in the retreading process.